Flights were suspended for at least an hour at London’s Heathrow, Europe’s busiest airport, after a suspected “drone sighting” in the area brought departures to a standstill on Tuesday evening.

The incident comes less than a month after suspected drone sightings caused chaos at Gatwick Airport, forcing flights to be cancelled and disrupting travel plans for 140,000 people.

“We are responding to a drone sighting at Heathrow,” Europe’s busiest airport said in a statement. “As a precautionary measure, we have stopped departures while we investigate. We apologise to passengers for any inconvenience this may cause.”

Heathrow and Gatwick reportedly spent millions of pounds on “military-grade anti-drone equipment” after the previous drone sighting scandal, which is still being investigated. The December incidents prompted public uproar when it was revealed that some of the drone sightings in the area could actually have been police drones.

Responding to possible crisis, British Transport Secretary Chris Grayling said he had spoken to the Home Secretary and Defence Secretary and confirmed that the military are “preparing to deploy equipment used at Gatwick should it prove necessary.”

The drama was short-lived, however, and flights resumed quickly, with flight-tracking website Flight Radar 24 tweeting that departures had begun again, but adding that there was a “backlog waiting to depart” the airport.

Conspiracy theory: The drone operator is Chris Grayling, and he’s stress testing UK airports to see how they cope in the event of no deal flight disruption! 😂#drone